At the center of the FBI’s investigation into abuses at the Los Angeles County Jail was a top-secret program known as Operation Pandora’s Box.

That investigation took a dramatic turn Wednesday with news that retired Los Angeles County Sheriff Lee Baca will plead guilty to a federal charge of making a false statement.

Here is a primer from The Times archives:

What was Operation Pandora’s Box?

It was launched after sheriff’s officials learned in the summer of 2011 that the FBI had enlisted Anthony Brown, an inmate in the Men’s Central Jail, to collect information about allegedly abusive and corrupt deputies.

In an unusual move, sheriff’s officials responded by moving Brown, a convicted bank robber, to a different jail under a fake name.

They assigned at least 13 deputies to watch him around the clock, according to documents reviewed by The Times. And when the operation was over, the deputies received an internal email thanking them for helping “without asking too many questions and prying into the investigation at hand.”

A Baca spokesman previously said that Brown was moved not to hide him from the FBI, but to protect him from deputies.

Prosecutors allege the goal was to prevent the FBI from talking to Brown.

What was the role of former Undersheriff Paul Tanaka, who was indicted on corruption charges last year?

An internal Sheriff’s Department email, written while Brown was allegedly being hidden from the FBI, states that Tanaka or one of his subordinates had to be present before deputies could move Brown.